Thermoelectric modules comprise a p-type thermoelectric element and an n-type thermoelectric element which are electrically connected in series via an electrode plate. A temperature difference of both sides of the pair of p-type and n-type elements develops a potential difference therebetween. Further if a current is passed through the junctions, heat is absorbed or generated depending on the direction of the current. The former phenomenon is termed the Seebeck effect and used for thermoelectric generation, for example, with the waste heat of refuse incinerators. The latter phenomenon is called the Peltier effect, which has found wide use, for example, in constant-temperature devices for semiconductor manufacturing processes and in thermoelectric cooling of electronic devices.
Such thermoelectric modules are produced conventionally by the process to be described below with reference to FIG. 23.
First, each of p-type and n-type thermoelectric materials is melted in a quartz ampule and then gradually crystallized in one direction to prepare an ingot, which is cut to obtain pieces of suitable size (e.g., several millimeters square). A p-type thermoelectric material 90 and an n-type thermoelectric material 91 are thus prepared as illustrated. To ensure effective joining, an Ni plating layer 92 is formed on each of opposite surfaces of each of the thermoelectric materials 90, 91, and a solder plating layer 94 is further formed over the Ni plating layer. Next, electrodes 98 are each prepared by forming a pattern of Cu directly on a ceramic substrate 96 serving as an electrically insulating material.
The thermoelectric materials 90, 91 are alternately arranged on the Cu electrode 98 on the ceramic substrate 96 in conformity with the pattern, and the other ceramic substrate 96 bearing the pattern of Cu electrode 98 is placed on the thermoelectric materials 90, 91. When the assembly is placed into a heater, the solder layers 94 melt, joining the Ni plating layers 92 of the materials 90, 91 to the Cu electrodes 98 on the ceramic substrates 96, 96.
Although FIG. 23 shows the p-type thermoelectric material 90 and the n-type thermoelectric material 91, each only one in number, thermoelectric modules usually comprise many pieces of each type of these materials although the number of components is dependent on the performance required.
With the conventional production process, the p-type and n-type thermoelectric materials are joined to the electrodes by soldering when the thermoelectric module is assembled, so that much labor is required for properly arranging small pieces of thermoelectric materials in position on the pattern and for the soldering step.
An object of the present invention is to provide a process including simplified steps for producing a thermoelectric module.
Another object of the invention is to provide thermoelectric elements which are useful for simplifying the process for producing a thermoelectric module.
Still another object of the invention is to provide a process for producing a thermoelectric element for use in simplifying the process for producing a thermoelectric module.